Was just about to post this. The answer to your problems is in your BIOS.

Windows XP is notorious for not wanting to run properly in AHCI mode. Depending on the type of BIOS you have, the option should look something like this.

Also, I would look into running Windows XP on a virtual machine. I have a pre-existing load that I took a Ghost image of and imported it into Vmware Workstation on my Windows 7 machine with 16GB. Having an SSD helps a ton also!

Yeah, you don't tell a Mac-addict to buy a PC and you don't tell a system builder to buy a Mac.

Also, this is a hardware problem so it can occur on any computer--even the Mac. I fix several Macs every year in addition to PCs. My friends with Macs that come to me for help never see it coming.

I've been building systems for 12 years now, and believe me when I say if you put a modest investment in to it you will build something that blows anything sold at a store out of the water for a fraction of the price.

I can tell you that this problem is likely hardware related. You possibly have a conflict with the RAM or an I/O device. The first thing you should do is remove one of your sticks of ram and try booting. This will eliminate the 32-bit limitation of your OS as a variable in the problem.

Also, try using each stick individually, this is a symptom of RAM failure, one of your sticks might be bad.

Things like internal memory card readers and network cards could be producing an error with the memory as well. Additionally, any USB devices you have plugged in can trip stop errors and boot up.

I recommend doing this: remove every external device you have connected to the computer (save the keyboard and monitor) and see if the error reoccurs. Next, you should try to remove all internal parts that you possibly can and try booting after you remove each part.
You should be down to just your CPU, motherboard, videocard (to connect to the monitor, if you have a build in videocard, remove the videocard too and try using the onboard for the monitor), one stick of RAM, and your hard drive that you are booting from.

If that doesn't work, you might have to reformat your hard drive. Your install could be busted.

Yeah, you don't tell a Mac-addict to buy a PC and you don't tell a system builder to buy a Mac.

Also, this is a hardware problem so it can occur on any computer--even the Mac. I fix several Macs every year in addition to PCs. My friends with Macs that come to me for help never see it coming.

I've been building systems for 12 years now, and believe me when I say if you put a modest investment in to it you will build something that blows anything sold at a store out of the water for a fraction of the price.

I have a few friends who build Hackintoshes--they end up paying about 1/4 to 1/8th the price for the same hardware. Insanity! I've never built one myself so I can't vouch for it.

I thought about triple booting with one of the OSs being OSX (thus making it a hackintosh) but I prefer AMD CPUs and it takes a lot more work to get OSX working on and AMD chip, since Macs are made pretty exclusively with Intels now.

also, xp doesn't natively support ahci for hard drives, which i'm guessing your new motherboard automatically chose. you'll have to switch the mode to ide initially and then change around some drivers if you want.

Telling a person who custom built their PC and is having a hard time getting the OS to install to guy buy a Mac is like telling someone having problems starting their $5,000 Honda Civic to go buy a $25,000 Lexus.